Le cours permet d'apprendre les bases de la planification urbaine à travers ses dimensions techniques, environnementales, sociales, économiques et symboliques. Le cours parle uniquement des villes africaines et même si celles-ci ont valeurs d'exemple pour les ville du Sud, voire toutes les villes, nous nous efforçons à remettre les problématiques dans un contexte africain.
Agriculture urbaine
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En provenance du cours de École Polytechnique Fédérale de Lausanne
Villes africaines I: Introduction à la planification urbaine
31 notes
École Polytechnique Fédérale de Lausanne
31 notes
À partir de la leçon
Le futur des villes ou comment planifier
Faire face au défi climatique qui change nos manières de faire la ville.
Rencontrer les enseignants
Jérôme ChenalDr
Faculté de l'Environnement Naturel, Architectural et Construit - ENAC
Today we'll talk about urban agriculture.
From the start, there are three questions.
When saying urban agriculture
it involves first and foremost acknowledging agriculture in cities.
It also involves planning spaces
and managing this activity.
In simple terms, urban agriculture is working the land
within the boundaries of a city, or the suburban area, most often.
It means taking advantage of the gaps, of unused land,
of everything that lends itself to agriculture.
Every possible resource is used: land, water,
and afterwards the markets to sell the products,
and all that happening within a city.
Urban agriculture appears to be an oxymoron,
two contradictory terms.
Why?
Because, on one hand, there is agriculture
strongly associated with rural areas, where agriculture is done,
and on the other hand the urban world,
which by definition is not rural, and so should not have agriculture.
The conventional definitions of cities
do not take agriculture into account.
There are also many people who are strongly opposed
to any agriculture within cities.
Why?
Because these activities should not take place
within the city boundaries.
Then, there is the opposite point of view,
acknowledging the vital importance of urban agriculture
for African cities today
and taking it into account in the planning process.
We'll see that there are some vexed issues
when planning agriculture within city boundaries,
one of them being land ownership,
but the social stakes are very high when it comes to urban agriculture.
Agriculture encompasses social aspects,
issues of space, of resources, of risks associated to it.
Let's go through every item one by one.
First, the social issue.
Extremely important in social terms:
it's a source of income that is not insignificant
for families that are, most of the time, the most vulnerable.
There is a question of empowerment behind this,
at least for some populations:
feeding oneselves,
even being able to sell some of their produce to make a bit of money.
It does have an impact to be considered on employment.
The issue of space is extremely important.
Why?
Because agriculture requires space.
Except for Cuba, where during the Special period
every flower pot was turned into a micro field planted with something
and every possibility to grow something in the city was seized,
the usual pattern is to use suburban lands.
Hence the question of space:
will I choose to build dense housing
or choose a more spread-out pattern
leaving room for agricultural production, meaning income generation?
This is one thing.
The second thing is that the denser a city,
the more pressure there is on land prices.
At some stage, prices are so high that it doesn't make any sense anymore
to grow a few vegetables, and it drives people even further.
The issues at stake here
is the opposition between spread-out cities and compact cities,
the issue of land use, land speculation,
but also simply of land markets, which, in most of the countries
and cities we are dealing with, are open markets,
meaning they fluctuate according to several factors,
but governments do not have the power
to regulate land prices, which poses a real problem
leading to pressure being put on urban agriculture.
Let's move now to the issue of resources.
Water is necessary.
Not only is there a need for a sufficient amount of water,
but this water needs to be good enough, too.
We'll see the potential health problems associated with urban agriculture.
The main health hazard
is that most of the time waste water is used.
Waste water are good in that they fertilize soils,
but there are also a certain number of germs which are pollutants
and will pass into the plants
and in turn into humans.
So, there is the issue of water quantity
and also of water quality, with a caveat regarding waste water
which can become a time-bomb.
It's both a fertilizer and a potential health hazard
in areas with urban agriculture.
These are just a few quick elements about urban agriculture.
There is much more to say, but we won't go further today.
I would just want you to bear in mind
that there is an indisputable use, a social use, to urban agriculture
but that it should be well thought through
depending on the density pattern you choose,
on the transportation options, or lack thereof,
and, in the end, on the ability to retain ownership
over a piece of land in times of growing land use pressure
in African cities.
In this week's classes where we start to see how to plan,
we realize there is a certain number of elements to take into account
and that these elements don't always go in the same direction.
Which means there will be choices to make,
between the different options, the different patterns:
spread-out cities with room for agriculture,
which is very good for climate change in tropical areas,
but on the other side in terms of public transportation,
of increased commuting, of the ozone layer,
since it is what it comes down to, it should be avoided at all cost.
A dense city pattern is good
but it means there is no room for urban agriculture,
which eliminates part of the resources.
What it all comes down to is that there is no panacea.
But one must be aware of the need to make judgment calls
between those elements that must be factored in
in our planning of future cities.
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